Draff and spent grain for cattle feed

What draff is

Draff is the spent grain left in the mash tun once the sugary wort has been drained off. It is mostly husk, protein, fibre and fat, with the starch largely gone into the wort. Wet draff is heavy with water, typically around 75 to 80% moisture.

As a rough guide, each tonne of dry malt mashed leaves behind something over a tonne of wet draff, because the grain soaks up so much water. A small distillery mashing one tonne a day makes several hundred tonnes of draff a year.

Why cattle farmers want it

Once the starch has gone, the remaining protein and fibre are concentrated. On a dry matter basis, draff typically carries something like 20 to 25% crude protein, plus digestible fibre and some fat. Dairy farmers use it as part of a ration alongside fodder and concentrates.

The protein content varies with the grain and how hard it was mashed, so ask a feed lab to test a few samples and share the results with buyers. Farmers pay more for a product they understand. Draff should be one part of a balanced diet planned by the farmer or a vet, never the whole ration.

How fast it spoils

Wet, warm and full of nutrients, draff is ideal food for moulds and bacteria. In a Scottish winter it might keep for several days. In Indian heat it can sour and start to smell within a day. Mould can follow soon after. Mouldy draff can carry mycotoxins that harm animals and should not be fed.

So the first rule is speed. Move draff off site the same day, or at most the next morning. Keep the hopper or trailer clean, covered and drained between loads.

Feed safety starts in the distillery. Keep draff free of foreign objects such as broken sieve parts, gaskets or plastic. A strong magnet over the draff conveyor is a cheap way to catch stray metal. Never let anything go into the draff hopper that you would not want a cow to eat, including floor sweepings and spilled cleaning chemicals.

If you use antifoam or enzymes, check with the supplier that they are acceptable in a feed co-product. Buyers increasingly ask. A clear answer makes a sale easier.

Ways to make it last longer

• Ensiling. Packed tightly in a pit or bag with air excluded, draff ferments to a stable, acidic silage that can keep for weeks.
• Pressing. A screw press drops moisture and weight, which cuts transport cost and slows spoilage.
• Drying. Drying gives a stable product but needs a lot of energy. It usually only pays at larger scale.
• Mixing with pot ale syrup. Larger distilleries dry draff with evaporated pot ale to make distillers dark grains.

For a craft distillery, a reliable local farmer who collects daily is usually the simplest answer.

Grain distilleries and DDGS

Grain distilleries running maize or broken rice produce a different feed. Because they often ferment on the grain, the solids are separated after distillation and dried with evaporated thin stillage into distillers dried grains with solubles (DDGS). DDGS is a traded feed ingredient in India for poultry, cattle and aquaculture.

DDGS from Indian grain plants varies with the feedstock and process, so buyers watch protein, fat and moisture closely. Our guide to handling pot ale and spent wash covers the liquid side of the same plant.

Setting up a draff contract

Write a simple agreement with your buyer. Cover the pick up schedule, who supplies the trailer, what happens on days they cannot come and the price per tonne or per load. Agree how weight is measured. Have a backup buyer or disposal route for the days the first one fails, because a full draff hopper stops the mash tun.

Hygiene matters both ways. Buyers' trailers should not bring dirt or pests into your site. Your draff should not carry cleaning chemicals. Make sure caustic rinse water never ends up in the draff hopper.

Thinking about value

Draff income will not change the economics of a distillery much, but it removes a disposal cost that could otherwise be large. A distillery that sells its draff has turned a waste problem into a small line on the income side. One that cannot sell it pays to have it hauled away. Our guide to how whisky is made shows where draff fits into the full process.

A first step

Before your first mash, phone three dairy farmers or feed traders within an hour's drive. Ask what they would pay for wet draff collected daily, what volume they could take and what testing they want. Their answers decide how big your draff hopper needs to be.

Common questions

What is draff?

Draff is the wet spent grain left in the mash tun after the wort is drained off. It is mostly husk, protein and fibre.

How much moisture does wet draff contain?

Wet draff is typically around 75 to 80% moisture.

How long does draff keep?

Only a day or so in Indian heat before it sours. Ensiling, pressing or drying can make it last longer.

What is DDGS?

Distillers dried grains with solubles, a dried feed made from the spent grain and evaporated stillage of grain distilleries.